Overload indicator for electrical circuits



Jan. 31, 1950. W, PARKERSON 2,495,981

OVERLOAD INDICATOR FOR ELECTRICAL CIRCUITS Filed Jan. 12, 1948 H5v 1 TLS l l f k1 4j /l lof-'5f- 11G- 14 7 @ff J4 C9 2 f5 l? .fsm-#Dime H zg Fuso:

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, FUSE Z7 230v Z 5V jme/MM HSV Y Jn- 1 4SUPPLY LNE LUi/lagm Parkerson Patented Jan. 31, 1950 OVERLOAD INDICATOR FOR ELECTRICAL CIRCUITS William Parkerison, Chicago, Ill.

Application January 12, 1948, Serial N o. 1,774

6 Claims. (Cl. 177-311) My invention consists in new and useful im C provements in an overload indicator for electrical circuits and has for its object to provide an arrangement for determining within reasonably narrow limits, the load which any customer of an electric company, for example, has imposed upon the line.

Another object of my invention is to provide an overload indicator which will function without interruption of service, in an electrical system, and to this end I provide a normally effective supply circuit and an auxiliary supply circuit, the former normally energizing a pilot lamp or other signal device and having interposed therein a delayed action circuit breaker, responsive to an overload extended over a predetermined period, and a controlling or circuit shifting relay which is operable upon the breaking of saidnormal cir cuit to energize said auxiliary circuit. Thus, in the event of an overload on the system, the signal lamp is extinguished and without noticeable interruption, the current is transferred from the normalsupply circuit to the auxiliary supply circuit. The extinguishment of the pilot lamp indicates to the inspector that the system has been subjected to an extended overload.

A further object of my invention is to provide a simple and practical overload indicator which will impose no resistance on the' load circuit such as might otherwise interfere with the maintenance of, satisfactory voltage and service at the load.

With the above and other objects in view which will appear as the description proceeds, my invention consists in the novel features herein set forth, illustrated in the accompanying drawings and more particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is a wiring diagram of one form of my invention designed to operate on two-wire, r115 volt, single phase service; and

Fig. 2 is a wiring diagram of a modiiied form of the invention adapted to operate on 115-230 volt, three-wire, single phase service.

Referring rst to Fig. 1 of the drawings, the numerals I and 2 represent the conventional supply lines leading from a source of electrical supply, not shown, to the load, the line 2 being preferably grounded att in the usual manner. Inu terposed in the supply line I, is a normal supply conductor 4 provided with a delayed action fuse 5 or other suitable circuit breaking device which is responsive to an overload imposed on the sysductor 6 having connected therein a pilot lamp 1, is shunted between the normal supply conductor 4 and the grounded supply line 2, said pilot lamp being responsive to the functioning of the delayed action fuse 5.

Anterior to the points of connection of th shunted signal conductor B, I provide a relay or control conductor 8 which is shunted between the normal supply conductor 4 and the grounded supply line 2, said conductor 8 having interposed therein a suitable relay 9 provided with a pair of spaced movable contacts I0 and II.

An auxiliary supply conductor I2 is connected in the normal supply line I at points anterior to the delayed action fuse 5 and posterior to the signal shunt conductor 6, respectively. The normal supply conductor 4 and the auxiliary supply conductor I2 are provided with switches I3 and I4 respectively which include the movable contacts I l! and II of the relay 9; These movable contacts I0 and I I are so arranged that when the relay 9 is energized, the contact I0 closes the switch I3 to complete the circuit through the supply line I and the normal conductor 4, and to l break the circuit in the auxiliary supply conductor I2. When the relay 9 is deenergized, the reverse takes place, and the movable contact II closes switch I4 and the contact IIJ opens switch I 3, thus deenergizing the normal conductor 4 and energizing the auxiliary conductor I2. Deenergizing of the conductor 4 also deenergizes the signal circuit conductor E and causes the lamp I to be extinguished.

The system just described is connected in a house circuit preferably at the point where service leaves the watt-hour meter. In` operation, as long as the delayed action fuse 5 is intact, the house load will be fed by completion of the circuit through line I, through conductor 4, and switch I3. The pilot light I in conductor 6 and the relay coil 9 in conductor 8 will both be energized. Should the customer impose too great a load on the line during an extended period of 10 or 15 minutes, for example, the delayed action fuse 5 will rupture, thus deenergizing the relay coil 9, dropping the contacts I0 and II, breaking the circuit through the normal conductor 4and extinguishing the pilot light l.

Simultaneously, service is .reestablished to the heuse load through the switch I4 in the auxiliary conductor I2, this being accomplished without noticeable interruption to the house service. However, the extinguishment of the pilot light 7 indicates that the allowable load for the delayed tem over a predetermined period- A signal ccn- 66 action fuse s has been exceeded.

This same principle may be applied with certain modifications in connection with 115-230 volt, three-wire, single phase service as will be seen from Fig. 2. In this ligure, I5, I6, and I1 represent three supply lines leading from a source of electrical supply to the house load, the line I1 being preferably grounded in the usual manner. I-Iere however, it is preferable, to employ two delayed action fusesand twosetsoflnormal and auxiliary supply conductors in order to adapt the invention to the three-wire service.

One normal supply circuit consists of a conductor I8 in circuit with the, supply` line I5;and`. having interposed therein a delayed action fuse;

I9 and a controlling switch 20. A second normal supply circuit comprises a conductor 2'I" in circuit with the supply line It."andhavinginter posed therein a delayed action fuse 22 anda controlling switch 23.

The auxiliary circuit for the line I5 includes a` Conductor 24 connected into linev l5 anterior t'o the fuse I9- and having interposed therein a controlling switch 25; A second auxiliarycircuit includesa conductor'ZG'# connectedfinto line IB, anterior to the fuse 22'- and having inter` posed hereinza controllingswitch 21.`

AL relay circuit isl shuntedacrossesupplylines I and I5v posterior tothe uses ISand 224A and includes' aV conductor 28 having` therein a' relay 29,' provided with two set'sfof' movablelcontact's 3Ii`y 3l, and 32, 33; included in'-tlie'-switches12ll', 25 and 23`; 2'I`respectively. Posteriortothe relay circuit, I provide a signal' circuit" consisting of a conductor shunted betweensupply'lines I5 4and IB` and having 'interposed therein f a pilot lamp 35.- Thus, boththe pilot lamp 35-andthe relay 29: are responsive to' either one of` the delayed action fuses I 9 or 22.'

The operation ofy thismodied form of my invention isf basically similar to=that`described in' connection withFig. l. Here, 115i volti service is normally available throughllines; I5 and IT- or lines IS and I'land 230 volti service-is available through lines [5T and ISS On 1,15Volt service, so-long as-thedelayedactionfuses I9' and 22 remaih'intact, the circuit is maintained through conductors I8" and' 2if, across contacts 39 and 32 of' switches 20* and 231 to the load, and the*V pilotlarnp 35E remains energized. Upon subjecting the' line to2 an extendedfoverload, one orv both ofk the fuses are ruptured, deenergizing the-relay'29 and-the pilot lamp 35, dropping the contacts130and32 ofthe relay to` break the'circuit throughlswitches- 2l]l and*- 23- and make theV circuit; in the'Y auxiliary switches 25' and'21through`contacts 3I1 and 33:;

On 230'volt service, so long aslthe fusesf I9 and 22 remain intact, the normal circuitiziscompleted through conductor I8 and' acrosslswitch 20' through contact 30; andthrough conductor 2'!` and across switch 23;v through contact 32'; The pilot lamp 35 anditherelay` 2.9will then beiv energized; Upon rupture of` either of the fuses I9 or 22 byoverloadingfthe" system, the relay 29`is deenergized andlthe pilotvlamp 35 extinguished, the deenergizingfof' the relay' 29 permitting the contacts 3D, 3|; 321, and' 33lto drop, breaking the-circuit through switches 20 and 23 of thenormal'circuit andv completing-the circuit'throughswitches 25 and'2'lin the-auxiliaryl circuit;

This same principle may be employedv withL equal advantageV in connection with a. syst-emv wired for 230 volt, threeewire, threephase'service. In fact, my inventionis readily'adaptable,

4 to various circuits and services with minor modifications to meet the particular needs of the individual situation.

From the foregoing it is believed that my invention may be readily understood by those skilled in the art Without further description, it being borne in mind that numerous changes ma be made in the details of construction without departing from the spiritiof the invention as set forth in the following claims.

I claim:

l. An electrical system for indicating overload,' comprising"two supply lines, a normal supply conductor and an auxiliary supply conductor in one of said supply lines, a signal conductor shuntedbetween said normal conductor and the otherv of saidsupply lines, a normally energized signal device connected in said signal conductor, acontrol conductor shunted between said normal conductor and said other supply line in parallel withr said signalI conductor, al relay connected insaid control: conductor,r said relayhaving movable contacts adapted" to close the circuit through` saidE normalv conductor andi open the circuit in said auxiliaryl conductor when the relay'is energizedland to open-thenormal circuit and close the auxiliary circuit1 whenr the relay-is deenergized'; and. a circuit-breaker in said-V normal conductor in seriesA withl said? signal and relay and responsive to overload onA the system.

2. An electrical system -for-indicating'overload, comprising twosupply# lines,v a normal supply conductor andan auxiliary'supply'con'ductor in one of' said# supply lines,l ar signal' conductor shunted between saidi normal conductor and the othery ofsaid: supply lines; a= normallyy energized signal device connected' in f said? signal conductor, a control conductor. shunted 4between said normal conductor and said other' supply. line in= parallel with saidsignall conductor, a relay connected in -saidlcontrol conductor, saidrelayhaving mov-` able contactsadapted'vto close-the circuit through said?. normal conductor andA open'. the circuit in saidfauxiliary conductorrwhenthe relay islenergized and to open the. normal circuit' and close theJ auxiliarycircuitf-when the relay isdeenergized, and ai delayedf action circuit' breaker-fin said normal conductor-inn` series, with said signal and' relay.'y and"` responsive to overload on the system.-

3. In a three-wire electrical system, meansffor indicatingl overload comprising a normaksupply conductor and"` an" auxiliary supply conductor connect'edzinV each'A of two of said" Wires; a signal device shuntedv across:4 said normal.y conductors andinormally energized'zthereby, switches in said normal and auxiliary conductors, a delayed. action circuit breaker in each ofzsaidnormal oonductorsvresponsive to; overload"l on the system, and meansresponsivertosaidcircuit breaker for controlling said switchesf tol shift" the` current from the; normal conductors.; to; the.- auxiliary conductors upon# breaking thei circuitl in either normal conductor'and thefdeenergizing of said signal .device- 41.-. An electrical system as claimedfin claim 3, wherein saidlast named means `comprises a relay coilsliuntedbetweensaid normal conductors for common control ofboth sets'ofswitches,

5. An electrical'systemfor indicatingoverload, comprisingv twoy supply lines, a normal supply conductor rand an" auxiliary supply conductor connected1V inoneof said lines, a' signal device 751 normally energizedthrough'- said normali supply conductor, switches in said normal and auxiliary conductors, a delayed action circuit breaker in said normal conducto-r, responsive to an overload on said circuit, and a relay coil operatively connected to said switches and shunted between said normal conductor and the other of said supply lines, said relay coil bein-g responsive to said circuit breaker for controlling said switches, to shift the current from the normal conductor to the auxiliary conductor upon breaking the circuit in the normal `conductor and the deenergizing of said signal device.

6. An electrical system for indicating overload comprising rst and second supply lines, a delayed action circuit breaker in the first supply line, a normally deenergized auxiliary conductor connected in said rst supply line adapted to ley-pass said circuit breaker, a normally energized signal device shunted between said first and second supply lines, posterior to said circuit breaker and responsive to the latter, a relay coil in parallel with said signal device and shunted between said rst and second supply lines, a nor- WILLIAM PARKERSON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,300,546 Armstrong Apr. 15, 1919 1,635,348 Samper July 12, 1927 2,317,030 Colvin Apr. 20, 1943 2,325,470 Bonanno et al July 27, 1943 2,414,932 Crockett Jan. 29, 1947 

